Unless otherwise indicated herein, the materials described in this section are not prior art to the claims and are not admitted to be prior art by inclusion in this section.
To provide cellular wireless communication service, a wireless service provider or “wireless carrier” typically operates a radio access network (RAN) that defines one or more coverage areas in which devices that are subscribed to service from the wireless carrier, such as wireless communication devices (WCDs), can be served by the RAN and can thereby obtain connectivity to broader networks such as the public switched telephone network (PSTN) and the Internet. A typical RAN may include one or more base stations (e.g., macro network cell towers and/or femtocells, such as base transceiver stations (BTS), access nodes, node-Bs, eNodeBs (eNB), or the like), each of which may radiate to define the coverage areas in which WCDs can operate. Further, each coverage area may operate on one or more radio carrier frequencies (e.g., radio frequency radiation patterns from a respective base station antenna). The base stations may then be coupled with a controller, which may then be coupled (e.g., directly or indirectly) with a switch or gateway that provides connectivity with a transport network such as the PSTN or the Internet. When a WCD, such as a cellular telephone, pager, or wirelessly-equipped computer, is positioned in a coverage area, the WCD communicates via a radio frequency air interface with the base station antennae of the coverage area. Consequently, a communication path can be established between the WCD and the transport network, via the air interface, the base station, the controller, and the switch or gateway.
In general, a cellular wireless system may operate in accordance with a particular air interface protocol or “radio access technology.” Examples of existing air interface protocols include Code Division Multiple Access (CDMA) (e.g., IS-95, IS-2000, 1×RTT, 1×EV-DO, etc.), Long-Term Evolution (LTE) (e.g., FDD LTE and TDD LTE), WiMax (e.g., IEEE 802.16), iDEN, TDMA, AMPS, GSM, GPRS, UMTS, EDGE, MMDS, Wi-Fi (e.g., IEEE 802.11), and Bluetooth. Each protocol may define its own procedures for initiation of calls, handoff between coverage areas, and functions related to air interface communication.
In accordance with the air interface protocol, each coverage area may operate on one or more carrier frequencies and may define a number of air interface channels for carrying information between the base station and served WCDs. These channels may be defined in various ways, such as through frequency division multiplexing, time division multiplexing, and/or code-division multiplexing (e.g., spread-spectrum modulation), for instance.
By way of example, each coverage area may define a downlink (or “forward-link”) control channel or other resource on which a base station may transmit control messages such as system information messages or page messages to WCDs. Each coverage area may also define an uplink (or “reverse-link”) control channel or other resource on which WCDs may transmit control messages such as registration requests and call origination requests (e.g., voice calls, data sessions, and/or other “calls”) to the base station. Each coverage area may then define one or more traffic channels (e.g., on the downlink) for carrying communication traffic such as voice data or other data between the base station and the WCD. In some examples, these links may be defined on one or more carrier frequencies or blocks of frequencies (e.g., frequency bands, such as 698-960 MHz, 1610-2025 MHz, etc.).
When the WCD seeks to engage in packet data communication with the RAN, the RAN (e.g., the WCD's serving base station) may assign one or more traffic channels or other connections for use by the WCD so as to enable the WCD to negotiate with the RAN and establish an active data connection. Once the WCD has established the active data connection, the WCD may then engage in a data communication session with the RAN. Types of data communication sessions may include, for instance, voice over Internet Protocol (VOIP) calls (e.g., push to-talk (PTT) and push-to-view (PTV) communication), file transfer protocol (FTP) sessions, and web browsing sessions, among others.